Bug Report: i am getting a fatal error while using this plugin at www.couplesinstitute.com

[seo1504]

PHP message: PHP Fatal error: Uncaught Error: Call to undefined function stcr\is_user_logged_in() in /www/ci2022_697/public/wp-content/plugins/subscribe-to-comments-reloaded/wp_subscribe_reloaded.php:778
Stack trace:
#0 /www/ci2022_697/public/wp-includes/class-wp-hook.php(308): stcr\wp_subscribe_reloaded->subscribe_reloaded_manage(Array, Object(WP_Query))
#1 /www/ci2022_697/public/wp-includes/plugin.php(256): WP_Hook->apply_filters(Array, Array)
#2 /www/ci2022_697/public/wp-includes/class-wp-query.php(3505): apply_filters_ref_array('the_posts', Array)
#3 /www/ci2022_697/public/wp-includes/class-wp-query.php(3787): WP_Query->get_posts()
#4 /www/ci2022_697/public/wp-includes/post.php(2417): WP_Query->query(Array)
#5 /www/ci2022_697/public/wp-content/plugins/advanced-custom-fields-pro/includes/class-acf-internal-post-type.php(401): get_posts(Array)
#6 /www/ci2022_697/public/wp-content/plugins/advanced-custom-fields-pro/includes/class-acf-internal-post-type.php(359): ACF_Internal_Post_Type->get_raw_p" while reading response header from upstream, client: 47.128.30.110, server: www.couplesinstitute.com, request: "GET /comment-subscriptions/?sra=s&srk=40b02d88a33ceb50216b1e63bc030f74&srp=8893&srsrc=f HTTP/2.0", upstream: "fastcgi://unix:/var/run/php8.1-fpm-ci2022.sock:", host: "www.couplesinstitute.com:19421"